Pyrolytic decomposition of silicon-bearing gas in fluidized beds is an attractive process for producing polysilicon for the photovoltaic and semiconductor industries due to excellent mass and heat transfer, increased surface for deposition, and continuous production. Compared with a Siemens-type reactor, the fluid bed reactor offers considerably higher production rates at a fraction of the energy consumption. The fluid bed reactor can be continuous and highly automated to significantly decrease labor costs.
A common problem in fluid bed reactors is fouling of interior components and surrounding reactor walls as silicon deposits form on the walls, temperature probe, pressure tap, seed nozzle, gas nozzles, and interior support structures. Another common problem is contamination of the fluid bed at high operating temperatures by materials used to construct the reactor and its components. For example, nickel has been shown to diffuse into a silicon layer from the base metal in some nickel alloys. Similar problems arise in fluid bed reactors configured for pyrolytic decomposition of a germanium-bearing gas to produce germanium-coated particles.